| Max Wisshak, Leif Tapanila: Current Developments in Bioerosion, p.149 (http://books.google.be/books?id=6Zy6xC4rB3oC&pg=PA149&lpg=PA149&dq=%22iceland+spar%22+naica&source=bl&ots=yNZUsRoVac&sig=m0Cp9OBbvp1TJtBm0syQM_c4puc&hl=nl&ei=6F_STviGJo6VOu3mveIJ&sa=X&oi=book_result&ct=result&resnum=4&sqi=2&ved=0CDYQ6AEwAw#v=onepage&q=%22iceland%20spar%22%20naica&f=false) |